Optimize unknown alpha paths

[deankarn]

optimizations of some code paths.

datetime/rfc3339_nano   time:   [37.431 ns 37.597 ns 38.258 ns]
                        change: [−4.7814% −3.5662% −2.3576%] (p = 0.05 > 0.05)
                        No change in performance detected.
datetime/rfc2822        time:   [58.006 ns 58.333 ns 59.638 ns]
                        change: [+0.0819% +1.6816% +3.2823%] (p = 0.22 > 0.05)
                        No change in performance detected.
datetime/yyyy-mm-dd hh:mm:ss
                        time:   [726.00 ns 728.12 ns 736.59 ns]
                        change: [+0.0474% +1.0165% +1.9704%] (p = 0.18 > 0.05)
                        No change in performance detected.
datetime/yyyy-mm-dd hh:mm:ss z
                        time:   [129.03 ns 130.16 ns 134.65 ns]
                        change: [+0.2906% +2.7469% +5.1737%] (p = 0.12 > 0.05)
                        No change in performance detected.
datetime/yyyy-mm-dd     time:   [915.05 ns 923.76 ns 958.61 ns]
                        change: [−23.202% −21.216% −19.241%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/yyyy-mon-dd    time:   [569.88 ns 573.40 ns 587.45 ns]
                        change: [−34.997% −33.893% −32.786%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/Mon dd, yyyy, hh:mm:ss
                        time:   [477.14 ns 480.01 ns 491.51 ns]
                        change: [+1.1712% +2.8519% +4.5495%] (p = 0.19 > 0.05)
                        No change in performance detected.
datetime/Sunday, April 18th, 2021
                        time:   [436.97 ns 439.74 ns 440.43 ns]
                        change: [+3.9001% +4.4618% +5.0200%] (p = 0.01 < 0.05)
                        Performance has regressed.
datetime/dd Mon yyyy hh:mm:ss
                        time:   [579.22 ns 583.31 ns 599.69 ns]
                        change: [−37.141% −35.904% −34.674%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/dd Mon yyyy    time:   [679.00 ns 684.05 ns 704.22 ns]
                        change: [−39.170% −37.919% −36.679%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/mm/dd/yyyy hh:mm:ss
                        time:   [1.1907 µs 1.1908 µs 1.1910 µs]
                        change: [−10.433% −10.226% −10.053%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/mm/dd/yyyy     time:   [1.3704 µs 1.3841 µs 1.4391 µs]
                        change: [−11.974% −9.6361% −7.2861%] (p = 0.03 < 0.05)
                        Performance has improved.
datetime/yyyy/mm/dd hh:mm:ss
                        time:   [337.61 ns 339.22 ns 345.62 ns]
                        change: [−21.510% −20.405% −19.309%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/yyyy/mm/dd     time:   [880.28 ns 881.11 ns 881.32 ns]
                        change: [−13.312% −13.061% −12.800%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/mm.dd.yyyy     time:   [511.35 ns 511.74 ns 513.29 ns]
                        change: [−46.052% −45.785% −45.540%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/yyyy.mm.dd     time:   [421.16 ns 421.19 ns 421.34 ns]
                        change: [−45.099% −44.981% −44.872%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/yymmdd hh:mm:ss
                        time:   [243.71 ns 244.31 ns 246.69 ns]
                        change: [−34.537% −33.993% −33.435%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/chinese yyyy mm dd hh mm ss
                        time:   [327.95 ns 328.02 ns 328.29 ns]
                        change: [−48.614% −48.471% −48.330%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/chinese yyyy mm dd
                        time:   [521.48 ns 523.39 ns 531.01 ns]
                        change: [−48.830% −48.254% −47.687%] (p = 0.00 < 0.05)
                        Performance has improved.
datetime/timezone_abbrev
                        time:   [1.6142 µs 1.6160 µs 1.6231 µs]
                        change: [−19.545% −19.214% −18.886%] (p = 0.00 < 0.05)
                        Performance has improved.